1. Field of the Invention
The present invention relates to a magnetic disk drive device. More specifically, the invention relates to a floating head slider of a magnetic head used for writing to and reading from data in a recording medium such as a magnetic disk.
2. Description of the Related Art
Magnetic disk drives devices require a magnetic head having a smaller amount of float away from a disk surface (hereinafter, flying height), to obtain a higher recording density, and accordingly, the flying height must be reduced to obtain a greater recording density. Also, due to on increase of the access speed, needed shorten the data search time, a substantially large inertia moment in the direction of access is exerted on the magnetic head and the head slider threof, and thus a low flying type head slider with the enhanced floating stability is required.
In connection with the above, the peripheral speed of rotation of a disk driven to rotate within the disk drive device is different at the radially inner side and radially outer side of the disk, and therefore, the slider must have a smaller fluctuation of the floating height thereof, depending upon the variations of the peripheral speed at radially different portions of the disk.
One example of the conventional floating head slider for the disk drive is disclosed in U.S. Pat. No. 4,734,803. The disclosed embodiment of the magnetic disk drive system employs a tapered flat plate head slider. Such a flat plate head slider includes a pair of side rails, tapered sections formed at the front end portions of the side rails, and a recess defined between the side rails. The side rails function as a pneumatic bearing, and thus have a positive pressure region at a portion along an axis of an air flow generated by a rotation of the magnetic disk. The positive pressure becomes highest at the upstream end portion oriented within the tapered section. The recess is made wide enough that it does not function as a pneumatic bearing. The head slider is biased by a spring load from the back thereof so that the magnetic heat remains in contact with the magnetic disk at a predetermined position thereof while kept inoperative in a contact start and stop (CSS) system. When the magnetic disk starts to rotate, the slider head slides on the disk and lifted at the front end thereof by the air flow generated by the rotation of the disk to thus float over the disk. This construction eliminates, the possibility that the flat head slider will drop onto the disk, and thus has stable flying characteristics.
The construction of such a flat head slider, however, whereby a floating force is generated at the tapered sections, makes it difficult to reduce or lower the flying height. Furthermore, the presence of the tapered sections leads to a possibility of a compression of floating gas within an enclosure of the magnetic disk drive, to thus cause a deposition thereof. This deposition tends to fall onto the disk during operation, to thereby cause head crashing.
In another known floating head slider having stable flying characteristics, a negative pressure generates a negative drawing force (suction force). In such a negative pressure type head slider, the recess has a tapered surface, or as an alternative, a stepped configuration, and the depth of the gap thereof is increased from the air inlet side to outlet side, to thus generate a drawing force. Namely, a negative pressure region is formed within the recess, to generate a drawing force for the disk, and thus the negative pressure type head slider provides a stable flying height regardless of variations of the peripheral speed of the magnetic disk.
In the above-mentioned negative pressure type head slider, however, organic vapor in the device tends to accumulate on the tapered sections or front end face of the step structure. Also, in the stepped configuration, due to an adiabatic expansion caused downstream of the step, floating gas tends to be deposited in the region downstream of the step. Furthermore, it is difficult to couple such a negative pressure type head slider with a rotary type positioner which is suitable for making the device compact, because the rotary type positioner causes a yawing of the head slider due to an angle thereof, and thus a distribution of the negative pressure by the negative pressure type head slider is varied due to this yawing, and this causes a significant amount of rolling, which in the worst case could cause the slider to drop down onto the disk.
One way of reducing or lowering the flying height is to narrow the widths of the side rails, but when the widths of the rails are reduced, the surface pressure at the unit area on the rail section is increased, which lowers the strength of the CSS. In the case of a generally utilized positive pressure head slider, if the depression force is maintained at a constant value, to maintain the ability to withstand external disturbances, the rail width can be narrowed in proportion to 0.033% of the power of the flying height. For example, when the flying height is halved, the surface pressure is increased by 60%. As a countermeasure this problem, a flat plate type head slider not having the tapered section can be used, but since the pressure of the air flow, over such a flat plate type head slider is offset toward the downstream side therof, the loading point also must be offset to coincide with the center of the floating force.
In current high performance devices designed to provide a high speed access, however, the loading point must be orientated in the vicinity of the center of the slider (position of center of gravity) to avoid a yawing of the head slider during the access operation due to a substantial acceleration of the speed thereof in the access direction.
Therefore, even with the flat plate type head slider not provided with the tapered sections, it is difficult to realize a high performance device designed to provide a low flying height and a high speed access.